sryanbruen Registered User
#1

After one of the weakest La Nina events on record, the models immediately turned around to an El Nino situation in 2017/18. Up to February, the models were showing a moderate El Nino and as I already said in the La Nina thread here:

http://www.boards.ie/vbulletin/showpost.php?p=102739020&postcount=21

Moderate El Nino is a good sign of a cold or blocked Winter but there is still a chance for a mild and wet Winter as with Ireland's weather, there is never a guarantee .

The CANSIPS model is showing a super strong El Nino to take place in 2017/18 but that's only two years after the previous super strong El Nino. There have been only three super strong El Nino events in existence so far. These being:

  • 1982/83
  • 1997/98
  • 2015/16

There is a long gap in between each of the above but how the CANSIPS is expecting a super strong El Nino to take place just two years after the previous one is very remarkable.

What's interesting to point out is the fact that each of the super strong El Nino events above had a remarkably mild Winter month with January 1983, February 1998 and December 2015. Obviously, January 1983 wasn't as extreme as the latter two but it was still very remarkable how mild it was.

We have not had a moderate El Nino since the beautiful Winter of 2009/10.. . It'd be amazing if we got a moderate El Nino this Winter and have a repeat of that Winter BUT we can all care to dream .

I think the CANSIPS is going way overboard with the super strong El Nino. I don't think it will come off and the most I can expect right now is a moderate El Nino. But hey, just because I don't think it will happen doesn't mean it won't happen.

God love us if it's a super strong El Nino and we have to suffer a month like December 2015 again .

EDIT: Also, it looks as though the cold blob in the Atlantic that has been stuck there since late 2014 will continue through 2017 which will make a negative NAO very difficult to happen. To add some optimism, the cold blob does not look nearly as cold or as large as it was in 2015, so very low chance we will get a month as wet as December 2015 next Winter.... at the moment that is from what I see.

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sryanbruen Registered User
#2

UPDATE: The signal is still very strong for an El Nino to take place during the course of 2017/18. The strongest signal is for it to a moderate El Nino.



Please to God don't be a super strong El Nino again!



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sryanbruen Registered User
#3

UPDATE: A moderate El Nino is still on the cards as predicted by the CFSv2 but the general consensus is quite close to a strong El Nino.



I've gathered some reanalysis here on Winters with a moderate & strong El Nino in regards to 500mb height anomalies.

Here is the reanalysis for Winters with a moderate El Nino:



This reanalysis shows that a moderate El Nino is a great contender for cold winters as the jet stream according to the low pressure distribution is on a very southerly track down towards the Mediterranean and with plenty of northern blocking, very stubborn northern blocking I should say. This northern blocking builds into parts of the UK and Ireland. This reanalysis shows a huge possibility for a cold Winter in 2017/18 if a moderate El Nino were to come off. Northerlies would not be able to take place in this pressure distribution as you would need a build of high pressure to center more towards Greenland and low pressure over Scandinavia. This reanalysis shows that easterly winds would be very evident through the Winter, something some of us have been wanting for so long!

But regardless of saying all this, you can't guarantee a cold Winter with a moderate El Nino as evident from Winter 1987/88 or Winter 1991/92 or Winter 2002/03. Let's just hope that if a moderate El Nino does take place, the NAO will go very negative and the QBO will become an easterly.

Meanwhile, here's the reanalysis for strong El Nino winters (not counting very strong El Nino winters like 1982/83, 1997/98 or 2015/16):



In contrast with the moderate El Nino reanalysis, this reanalysis shows a very awful pattern. The reanalysis shows some northern blocking but way over to Canada and western Greenland along with a very deep area of low pressure extending from northern Russia all the way to Mexico with Ireland included in this. In fact, Ireland is centered near one of the places where the low pressure is at its worst. It's clearly evident here that a strong El Nino is most certainly not a good sign for a cold Winter, far from it actually. Instead, a very stormy Winter could well take place if a strong El Nino were to take place. There has not been a strong El Nino since 1972/73, so we're overdue a strong El Nino at this stage and given how dry this past Winter was, we're due a very stormy Winter I think.

These are only predictions based on previous occurrences of moderate and strong El Ninos, not in any way a guarantee.

Reanalysis charts sourced from https://www.esrl.noaa.gov/psd/cgi-bin/data/composites/plot20thc.v2.pl

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sryanbruen Registered User
#4

I found this interesting graph today which shows the NAO for December to February (Meteorological Winter) from 1900 to 2012 or Winter 1899/1900 to Winter 2011/12.



Out of the moderate El Ninos that have been recorded, a negative NAO has occurred during Winter 2009/10, Winter 2002/03 (though very weak negative NAO), Winter 1987/88 and Winter 1963/64. So this means that a negative NAO has taken place in all moderate El Nino winters since 1963 with the exception of 1988/89 and 1991/92.

If a moderate El Nino were to take place, we would have a 66% chance of a negative NAO to take place. Therefore, that means 34% chance of a positive NAO to take place. So with a moderate El Nino, it is much more likely for a negative NAO to happen than a positive one which is good for cold winters.

The graph shows that Winter 2009/10 had the most negative NAO within the last 100 years which is very interesting and Winter 1962/63's NAO is the 3rd most negative.

I'll hopefully find the AO for the same period as this graph represents with the NAO. Let's hope there is some good correlation once I do though I'd highly doubt that knowing our climate never has any guarantees and will always surprise us with exceptions to our theories .

NAO graph sourced from: https://www.rmets.org/sites/default/files/abstracts/Mar/16032013-burt.pdf

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